Unpacking "git push –set-upstream origin" for Software Teams

As applications grow in complexity, leveraging Git‘s powerful branching workflows becomes critical for managing large, distributed software projects. At the heart of these workflows lies the concept of remote tracking branches and the git push --set-upstream command.

This comprehensive guide will unpack what exactly --set-upstream does under the hood and why setting up this remote tracking is so vital for development teams.

The Role of Remote Tracking Branches

To understand --set-upstream, you first need to grasp the idea of remote tracking branches. These are read-only local references that represent the state of remote branches.

In the above diagram, origin/feature is the remote tracking branch for the feature branch on the remote repository origin.

This remote tracking branch allows Git to:

• Know the commit history of origin/feature
• Compare local branch state vs the remote
• Seamlessly push/pull changes between interconnected local and remote branches

Without these tracking references, Git has no record of remote branches locally. This complicates branch synchronization and collaboration.

That‘s why setting up remote tracking is so essential – it binds local branches to related branches on remote repositories.

Configuration is Key with git push –set-upstream

While you can manually create remote tracking refs, the git push --set-upstream shortcut streamlines this process by automatically configuring the upstream remote branch to track.

Here is the command format:

git push --set-upstream origin <branch_name>

For example, running:

git push --set-upstream origin feature  

Will:

1. Push the local feature branch to remote repository origin
2. Configure origin/feature as the remote tracking branch for the local feature branch

Now Git knows:

• Where to push local feature branch commits
• How to compare local vs origin/feature remote branch

This automatic configuration is why --set-upstream is so useful – it sets up the tracking relationship in one command.

Without it, you must manually create remote tracking refs using verbose syntax:

git update-ref refs/remotes/origin/feature master 
# or 
git config branch.feature.remote origin
git config branch.feature.merge refs/heads/feature

Key Takeaway:

The --set-upstream option handles all this remote tracking configuration so developers don‘t have to manage refs manually.

Common Branch Configuration Scenarios

Now that you understand how --set-upstream works, let‘s walk through some common scenarios you may encounter when configuring branches.

Fresh Local Branch

When starting a new feature branch, set up remote tracking right away to connect it with the related branch on the remote repository.

# Create new local branch 
git checkout -b feature 

# Set remote tracking 
git push -u origin feature

This best practice avoids "detached HEAD" issues down the line.

Existing Local Branch

If you forget to configure upstream tracking when creating a branch, use --set-upstream to add it later:

# Develop on existing branch 
git checkout feature

# Realize tracking wasn‘t set up  

# Set remote tracking to origin  
git push -u origin feature

This flexible command works whether branch exists only locally or on remote already.

Syncing Forked Repository Branches

A common scenario when contributing to open source projects is needing to push a forked repo branch to the upstream repository:

# Clone forked repo
git clone github.com/my-org/project

# Make changes to branch 
git checkout -b patch-1 

# Push patch to my fork
git push origin patch-1  

# But also need to sync with upstream!
git push --set-upstream upstream patch-1 

The last command synchronizes your fork branch with the upstream repository. This allows maintainers to easily review pull request diffs.

Pro Tip: To simplify upstream syncing, set the upstream remote locally:

git remote add upstream https://github.com/original-org/project

Now upstream can be referenced instead of full URL each push.

Common Upstream Branch Pitfalls

While improperly configured upstream tracking can cause frustrations down the line, being aware of a few potential issues helps avoid headaches:

Pushing Old Local Commits

By default, git push uploads all commits on your local branch since it diverged from the remote branch:

This can be problematic if you rebase/amend old commits before pushing upstream. Your new changes will now conflict with the old commits!

git push # old local commits re-pushed unexpectedly!

Solution: Be explicit if only pushing latest commit:

git push origin feature:feature # push tip of feature branch only 

Or, reset tracking branch to origin state before new work:

git fetch -p # get latest remote commits 
git reset --hard origin/feature # match local branch to origin 

Now git push will only upload new diffs.

Deleting Stale Remote Branches

When you delete a branch on a remote repository, the remote tracking branch locally does not get deleted automatically. This can cause errors down the line:

git push origin feature

# ERROR - remote origin branch was deleted!
error: unable to push to unqualified destination

Solution: Manually prune stale remote tracking refs with:

git remote prune origin --dry-run # preview deletions  
git remote prune origin # actually delete  

This keeps local repository state in sync with remote branches.

Complex Push/Pull Histories

Juggling multiple interconnected local and remote branches can vastly complicate upstream tracking:

If branches get crossed or pull locations switch, your push targets can get muddled.

Solution: Always verify current upstream configuration with:

git branch -vv # view tracking status  
git config branch.<branch>.remote # inspect branch config

Then reset any incorrect upstreams:

git branch --set-upstream-to origin/<branch> 

The key is carefully mananing upstream links as your branches evolve.

Enabling Advanced Git Workflows

Upstream tracking branches serve as the foundation for more advanced Git workflows used to manage large, long-running projects among distributed teams.

A common example is Gitflow. The Gitflow model leverages tracking branches so development teams can collaboratively work on features and releases in parallel:

Without tracking branches acting as the central conduits between local and remote repositories, intricate workflows like Gitflow would not be possible.

So while setting up a remote tracking branch via git push --set-upstream may seem like a mundane configuration task, it unlocks the true power of Git!

Wrap Up

Whether needing to share feature branches with team members or integrate forked repositories, properly establishing remote tracking upstream branches is critical.

The git push --set-upstream shortcut streamlines connecting local branches with remote counterparts – forming the vital link that enables a host of Git workflows essential for large, distributed software initiatives.

With this comprehensive guide, you now have the complete picture of how upstream branches function under the hood along with practical guidance for configuring tracking branches in real-world scenarios.